Glycosyltransferases are responsible for synthesis of cell surface glycoproteins and glycolipids. Human plasma contains many glycosyltransferases; some of these are responsible for synthesis of specific blood group substances (A1, A2, B, H), and others play a role in synthesis of glycoproteins and glycolipid. A specific N-acetylgalactosaminyl transferase, (A-enzyme) which synthesizes blood group A-substance, exists in blood type-A subjects, while a specific galactosyltransferase (B-enzyme), which synthesizes blood group B-substance, exists in blood type-B subjects. The objective of the proposed project is to determine: 1) purification and structural characterization of blood group A1-enzyme, A2-enzyme and B-enzyme and an enzymatically inactive but immunologically cross-reactive, protein in O-plasma; 2) the molecular properties and immunologic characteristics of other carbohydrate transferases in human blood; and 3) the underlying genetic mechanism of expression of common (ABO, MN) and rare (Am, Ax, Bombay) blood types. The project consists of the following studies: 1) purification and structural characterization of blood group A1-enzyme, A2-enzyme and B-enzyme and an enzymatically inactive but immunologically cross-reactive protein existing in O-plasma; 2) purification and study of enzymatic, chemical and immunologic characteristics of N-acetylgalactosaminyltransferase from Am and Ax plasma, and examination of membrane components in A2, Ax and Am; 3) purification and chemical and immunologic characterization of other carbohydrate transferases.